<?php$key = "69a9112367f2fe155642490ab8cd184f"; //thay bang checksum key$cs=sha1($key.$_GET['session'].'.'.$_GET['order_no'].'.'.$_GET['status']);if($cs == $_GET['checksum'] && $_GET['status'] == 1) //status = 1 da thanh toan{	$out = fopen('invoiceGET.txt', 'a');  	fwrite($out, "\r\nDate: ".date("Y-m-d H:i:s"));	fwrite($out, "\r\nREMOTE ADDR (expect 118.69.206.8) : ".$_SERVER['REMOTE_HOST']);	fwrite($out, "\r\nOrderNo: ".$_GET['order_no']);	fwrite($out, "\r\nState: ".$_GET['status']);	fwrite($out, "\r\n");	//... so on...	fclose($out);}else{	$out = fopen('invoiceGET.txt', 'a');  	fwrite($out, "\r\nDate: ".date("Y-m-d H:i:s"));	fwrite($out, "\r\nREMOTE ADDR (expect 118.69.206.8) : ".$_SERVER['REMOTE_HOST']);	fwrite($out, "\r\nChecksum sai");	fwrite($out, "\r\n");	//... so on...	fclose($out);}?>